A team led by Leopold Eckhart of the Medical University of Vienna in Austria made the discovery by comparing human, chicken, and green anole lizard genomes.

The genome of the lizard was found to contain six different genes for hair keratin, the protein from which mammal hair is made.

The genes were expressed most strongly in the lizard's toes, indicating that the first hair genes played a role in claw formation, the study team reports in tomorrow's issue of the Proceedings of the National Academy of Sciences.

"At least two of these hair protein keratins are formed in the growth zones of the claws," Eckhart said.

While the role of the anole lizard's four other hair genes remains unclear, they were likely related to the growth of scales, the study team said.

The chicken genome revealed a single hair gene. It's unclear what that gene is for, if anything.

Hair-Raising Creatures

The finding suggests that modern birds, reptiles, and mammals—as well as dinosaurs—shared an early common ancestor that had claws built from hair keratin, Eckhart said.

"Actually, it may be more appropriate to call these proteins claw keratins, which later acquired an additional role in hair," he said.